Lemma 6.21 (See [1]}.) 
 Assume that \(d \ge 3\) .
Consider a parameter array (REF ) over \(\mathbb {F}\)  with fundamental constant \(\beta \) .
Then there exist scalars \(\gamma \) , \(\varrho \)  such that
\(\gamma &= \theta _{i-1} - \beta \theta _i + \theta _{i+1} && (1 \le i \le d-1),\\\varrho &= \theta _{i-1}^2 - \beta \theta _{i-1} \theta _i + \theta _i^2 - \gamma (\theta _{i-1} + \theta _i)&& (1 \le i \le d).\) 

